The present invention relates to a method for converting aromatic compounds having substituent(s) and having a relatively large molecular size.
As known, zeolite is used as a catalyst for conversion of aromatic compounds having substituent(s), for example, for xylene isomerization, toluene disproportionation, etc. It is known that zeolite, especially mordenite-type zeolite is used for conversion of aromatic compounds having at least 3 substituents (Japanese Patent Laid-Open No. 14430/1983).
Zeolite is a porous crystal of which the pores are uniform and have a molecular-level size. It can be a catalyst having good activity and selectivity for conversion of aromatic compounds having a relatively small molecular size, for example, for xylene isomerization, toluene disproportionation or the like, and is so used in some industrial-scale plants. However, for conversion of large-size molecules, using zeolite is often problematic in that the reactant molecules could not penetrate into the zeolite pores, or even if having penetrated thereinto, they could not diffuse rapidly through the pores to receive satisfactory conversion activity. On the other hand, among many kinds of zeolite, pentacyl-type zeolite, mordenite-type zeolite, xcex2-type zeolite, and faujasite-type zeolite are widely used.
xcex2-type zeolite and faujasite-type zeolite have pore apertures with the largest size of these zeolites. However, they have channels with large-size aperture and also have very large spaces formed by intersecting channels. Therefore, their drawback is that some undesired molecules (high-boiling-point compounds) are formed in the intersections of the channels with large space, and the undesired molecules thus formed therein clogs the pores to cause activity depression.
Being different from these catalysts, mordenite-type zeolite has no intersection of large-pore channels, and few undesired large-size molecules can be formed therein. But the aperture size of the pores therein is not so large and it is not so effective for converting large-size molecules. Accordingly, the object of the present invention is to solve the prior art problems, precisely to provide a highly-active, selective and long-life method for converting aromatic compounds having a large molecular size, concretely, for converting at least one aromatic compound selected from (a) aromatic compounds having at least three substituents, (b) aromatic compounds having two substituents of which at least one is a halogen or has at least 2 carbon atoms, and (c) naphthalene or anthracene derivatives having substituent(s).
To attain the subject matter as above, the method of the invention principally comprises contacting at least one aromatic compound with a zeolite-containing catalyst, wherein the zeolite is characterized in that;
(1) the minimum value of the pore aperture diameter of the major channels therein is larger than 0.65 nanometers (hereinafter referred to as nm), or the maximum value thereof is larger than 0.70 nm, and
(2) the major channels do not intersect any others with larger apertures than an oxygen 10-membered ring;
and the aromatic compounds are at least one compound selected from the group consisting of;
(a) aromatic compounds having at least three substituents,
(b) aromatic compounds having two substituents of which at least one is a halogen or has at least 2 carbon atoms, and
(c) naphthalene or anthracene derivatives having substituent(s).